The present invention relates generally to lasers and, more particularly, to a low cost, low power solid-state laser which generates a visible laser beam suitable for use in numerous applications, including surveying, measurement, and equipment control in the construction and agricultural industries.
Presently, many laser based instruments utilize conventional visible light helium neon (HeNe) plasma tubes as a source of the laser beam. For further advancement and improvements in such laser based instruments, laser sources consuming much less electrical power, occupying much smaller spaces and preferably also costing less money, need to be developed.
One promising alternative to the HeNe plasma tubes for these applications is the recently developed visible laser diode, coupled with a lens system for shaping and collimating the laser beam. Unfortunately, manufacturers of these visible light laser diodes have had difficulty in commericalizing them and their emission wavelength tends to be just inside the visible band in the 670-690 nanometer (nm) region. As a consequence, for an "average" observer, anywhere from 22-68 milliwatts of beam output power is required to visibly equal the three milliwatt output power of the helium neon plasma tubes. Such power levels do not appear to be forthcoming in the near future.
Another possible replacement for the helium neon plasma tubes are solid-state lasers, for example as disclosed in U.S. Pat. Nos. 4,653,056, 4,656,635, 4,665,529 and 4,701,929. Unfortunately, these devices are generally concerned with higher power outputs and, due to the power and quality restrictions placed on the output beams generated by these devices, can only be purchased at a much higher price than the helium neon plasma tubes.
Accordingly, there is a need for an inexpensive laser which produces visible light at a level comparable to that of the three milliwatt helium neon plasma tubes presently used, which also consumes much less electrical power and occupies a much smaller space.